Fuel cell systems are increasingly being used as power sources in a wide variety of applications. Fuel cell systems, for example, may be used as replacements for vehicle internal combustion engines (ICE).
A proton exchange membrane (PEM) fuel cell includes a membrane electrode assembly (MEA) that is sandwiched between conductive anode and cathode plates. This membrane functions as a proton conductive electrolyte membrane in a water containing state. In a dry state, however, its proton conductivity decreases, thus causing a decrease in power output. Therefore, a fuel cell system equipped with this type of fuel cell is often designed to humidify reaction gases (anode gas and cathode gas) supplied to an anode and cathode of the fuel cell by a humidifier so that the membrane can maintain proper humidity.
To produce electricity through an electrochemical reaction, hydrogen (H2) is supplied to the anode and oxygen (O2) is supplied to the cathode (via air). In a first half-cell reaction, dissociation of the hydrogen H2 at the anode generates hydrogen protons H+ and electrons e−. The membrane is proton conductive and dielectric. As a result, the protons are transported through the membrane while the electrons flow through an electrical load that is connected across the membrane. In a second half-cell reaction, oxygen O2 at the cathode reacts with protons H+, and electrons e− are taken up to form water H2O.
Because fuel cells have become viable for widespread commercial use, cold weather performance characteristics of fuel cells have become more important. The ambient temperature tolerance specification for certain vehicles, for example, typically includes temperatures between −40° C. to 52° C. Liquid and vapor water within the fuel cell system, however, may present issues for cold weather operation of the fuel cell. The fuel cell stack humidification systems and water generation at the cathode during operation generally ensure that water in a liquid or vapor state will exist in almost all parts of the fuel cell stack during dwell times. At one atmosphere and temperatures below 0° C., water freezes and may block the flow passages of the fuel cell stack and the fuel cell system balance of plant. These blockages may hinder fuel cell system operation.